From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D096576EB8; Wed, 9 Sep 2026 15:53:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.156.1 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788969234; cv=none; b=NfwWvkdb6KtBKNStvdqyo+kMrRA9Z19IRee3digS2QS9gc0+po/rLeV2zqMp3yw74/wgyY1LKOV/Aopz+TQ/x6hSO6XCj1/Bb+PHVJoTqtK+IAJAL/hXtUit2sIfh5k0XTffF9SiyjbHAeYnqK9sC9rd7NNcMNp16mH5f664NPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788969234; c=relaxed/simple; bh=dUjHsZuyDv1l8FbpCpEgVt+StsM7dxMMLWPLdFQAmW0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NCxrsAXLnmcd4uM8n7PlRgsp0uUZlU73Ka8xPFgNDBy0m9s0I85PWhjsWMuysxdkVqT044PbVthdQzfYmeKIhgAwVBnHipTCGLvK3lwPiXkzG6Cwy8teEFFe/xwpT2GxiihSQ7LOY7yL5p0VMozfR0YDKXcCJduIGO+Eh+HQeas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=FkZShthZ; arc=none smtp.client-ip=148.163.156.1 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="FkZShthZ" Received: from pps.filterd (m0353729.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 689B1hXA1930950; Wed, 9 Sep 2026 15:53:24 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=9fEv8C VQ+LcrjyrEyKWNY8tE1ZC5nOC4fuPxuTwwtWQ=; b=FkZShthZPf6z6Inxuhf+uF iNXUzguRjPZq6PaXhqShCZ3McDp20T3UU5KU3cjMrWdZqtNCUuSuqfdkm8GvIvLF dd72+XGKDtIjz69shK+IZlKQChWqyKHmF6exXT0UkgZBSqDxfU9Ur7ERBXMUX80P s0bhDfhWZtFY8AxXcf0pCGiGI5KikMBri/OGHlqKcjofQOFEa0vOHAVhylAiOQpt uCOLt6833VHDacYxqLq1mLTEtUp5aex8n856rgslbajZo+ccvWXcR2TgU4TdVmIw 4EHKN7jBzQE3ENXFaCKAqQK2azDDhu9EJCVqra+ip00luEloiWqmnR79lR7H0gcw == Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4ggbqk6vp0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 09 Sep 2026 15:53:23 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 689FfE6N015367; Wed, 9 Sep 2026 15:53:22 GMT Received: from smtprelay05.fra02v.mail.ibm.com ([9.218.2.225]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4ggwswb807-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 09 Sep 2026 15:53:22 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (smtpav01.fra02v.mail.ibm.com [10.20.54.100]) by smtprelay05.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 689FrJXq50987368 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 9 Sep 2026 15:53:20 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D9F5A2004B; Wed, 9 Sep 2026 15:53:19 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4CF0E20043; Wed, 9 Sep 2026 15:53:10 +0000 (GMT) Received: from [9.61.255.18] (unknown [9.61.255.18]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 9 Sep 2026 15:53:09 +0000 (GMT) Message-ID: <30360c50-0238-40e8-b598-bdfda1141cc8@linux.ibm.com> Date: Wed, 9 Sep 2026 21:23:06 +0530 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 02/22] coredump: refuse negative skips To: Christian Brauner , linux-fsdevel@vger.kernel.org Cc: Jacob Lalonde , Josef Bacik , Jann Horn , Alexander Viro , Jan Kara , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Omar Sandoval , Jacob Lalonde , Shuah Khan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20260820-work-coredump-sparse-v2-0-ba32dd718c51@kernel.org> <20260820-work-coredump-sparse-v2-2-ba32dd718c51@kernel.org> Content-Language: en-US From: R Nageswara Sastry In-Reply-To: <20260820-work-coredump-sparse-v2-2-ba32dd718c51@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: pYL1X5j4L64D3lhY8GC7_PxezJajFPeA X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA5MDE3MyBTYWx0ZWRfXyZQ2yeCYTZ8Y 0zY5ztZt9jhIlCwPuIHMWYJZeFMN1RfSvZmQxlYKHYhZCliMI/1/l/3Wg0EpWXDDd6lWozX46Rp BOsUhsvxP3K7Gf6k9YxbUWZBPcLY48o= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA5MDE3MyBTYWx0ZWRfX5MyolTbYyMTx 81rdDfK4pUyI4nx4v6Y9Tq/r/gVfH0lueULm43ZNa2On7UJUzNwVwdVblnzuc6TdwypX9OVkabd mY7Y+a3Um2ewoWxHnuzkeZMU9B9ZEx8zXreAkdyeB0s9N4qbY4sE3Mi+N9nw47/d2BRpkyMNGvD 3NamjGc8COyszi5eNpC2WHmCm6ZnIaCNR9nVGU8PKzrDMBSZz7UZmsQZ2GC97VMvBlLdIC1rSRX cnRoYJFT+Rf7HW7PJ/28KPLDCHwRT7HIo66pa7r9Oacak+UAvogwSvhdsx8cRtWmtDzjGv5q3Tx MRgAeULZKoh4YyzTCo7msiB5MQSn0j7ly8YqteQYeKytKoC6USiarP/25m9uwlz0MZyki4TDtFE 9HQGoeP/j1znxi3DPlsn/xA5Dz4ToJDJEyWtDxCPse+ktxUKAo6Dlm+UeqHdrTyl+tA5+qewgyB 79OOPB5Pjo8vswDjYfA== X-Authority-Analysis: v=2.4 cv=JaKMa0KV c=1 sm=1 tr=0 ts=6aa180f3 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=0fa85O3lyfMzuANSHggA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: x7FvKhawyt97Kk1EQB6_XHSAe9xWv9Jr X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-08_03,2026-09-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 phishscore=0 impostorscore=0 lowpriorityscore=0 adultscore=0 bulkscore=0 priorityscore=1501 suspectscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609090173 On 20.08.2026 4:39 AM, Christian Brauner wrote: > The dump_skip_to() helper calculates a relative skip based on the > absolute positon of the coredump: > > cprm->to_skip = pos - cprm->pos; > > That's easy to mess up for callers and one already did. This risk > endless zero PAGE_SIZE loops or overwriting already written coredump > data thereby corrupting the dump. > > I don't think skipping backwards has any meaning. So warn and refuse. > > Signed-off-by: Christian Brauner (Amutable) Tested-by: R Nageswara Sastry System: ppc64le LPAR (IBM POWER), Linux 7.3-rc2 > --- > fs/coredump.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/coredump.c b/fs/coredump.c > index e68a76ff92a3..ac4e922c9cb9 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -1261,6 +1261,8 @@ EXPORT_SYMBOL(dump_emit); > > void dump_skip_to(struct coredump_params *cprm, unsigned long pos) > { > + if (WARN_ON_ONCE(pos < cprm->pos)) > + return; > cprm->to_skip = pos - cprm->pos; > } > EXPORT_SYMBOL(dump_skip_to); > -- Thanks and Regards R.Nageswara Sastry